Accessible markup demonstration

<divclass="demo"role="application"><p>
Clicking the button will show the loading indicator for a set time. The indicator has been marked up with all the appropriate ARIA attributes.
</p><buttonclass="demo-toggle demo-off">Start example</button><br><divclass="o-loading o-loading--dark"role="progressbar"aria-valuetext="loading"tabindex="0"></div></div>